This working paper is one in a series that examines how public funds can mobilize private investment to help meet the significant needs of developing countries. Two public actors are examined: The Overseas Private Investment Corporation (OPIC) and the Export-Import Bank of the United States (Ex-Im Bank). Together these institution intermediated 37 per cent (over $2 billion) of total US assistance to developing countries for climate change activities from 2010 to 2012 by exclusively financing private sector projects. The paper draws from the experiences of OPIC and Ex-Im Bank to inform other public financial institutions and mechanisms – including the Green Climate Fund and public intermediaries of climate finance – about how financial instruments can be employed to promote private sector investment in climate-relevant sectors.